The seed germination spectrum of alpine plants: a global meta‐analysis

Abstract

Summary Assumptions about the germination ecology of alpine plants are presently based on individual species and local studies. A current challenge is to synthesise, at the global level, the alpine seed ecological spectrum. We performed a meta‐analysis of primary data from laboratory experiments conducted across four continents (excluding the tropics) and 661 species, to estimate the influence of six environmental cues on germination proportion, mean germination time and germination synchrony; accounting for seed morphology (mass, embryo : seed ratio) and phylogeny. Most alpine plants show physiological seed dormancy, a strong need for cold stratification, warm‐cued germination and positive germination responses to light and alternating temperatures. Species restricted to the alpine belt have a higher preference for warm temperatures and a stronger response to cold stratification than species whose distribution extends also below the treeline. Seed mass, embryo size and phylogeny have strong constraining effects on germination responses to the environment. Globally, overwintering and warm temperatures are key drivers of germination in alpine habitats. The interplay between germination physiology and seed morphological traits further reflects pressures to avoid frost or drought stress. Our results indicate the convergence, at the global level, of the seed germination patterns of alpine species.

Seeds and Seedlings in a Changing World: A Systematic Review and Meta-Analysis from High Altitude and High Latitude Ecosystems

“…There is also a lack of studies regarding the early life-history stages of tropical alpine species. These findings partially contrast with the reported trend for global alpine research, where most of the studies during the last decade occurred in Asia, particularly in China, but coincide with the lack of studies from the southern hemisphere [ 44 ] or tropical alpine regions [ 20 ].…”

“…Temperature and water availability, two of the changing environmental factors, are the main drivers of the early life-history stages of high altitude and high latitude plants [ 17 ]. Before germinating, many alpine and arctic seeds need to experience cold temperatures (a cold stratification), generally provided during winter under the snow [ 17 , 18 , 19 , 20 ]. Soil warming above ambient temperatures, combined with soil moisture availability after the snowmelt, may trigger the germination of many species [ 20 , 21 , 22 ].…”

“…Before germinating, many alpine and arctic seeds need to experience cold temperatures (a cold stratification), generally provided during winter under the snow [ 17 , 18 , 19 , 20 ]. Soil warming above ambient temperatures, combined with soil moisture availability after the snowmelt, may trigger the germination of many species [ 20 , 21 , 22 ]. Rapid germination in early spring allows seedlings to establish in the most favorable part of the year [ 17 , 21 ].…”

Germination at Extreme Temperatures: Implications for Alpine Shrub Encroachment

“…For most species, mean seed germination was less than 10% despite cold-stratification, scarification of the hard-coated seeds in the Fabaceae family, adequate time under experimental conditions and accounting for non-viable seeds with post-experiment cut-tests, of which there were very few. This suggests a deep inherent dormancy in many of these species, perhaps requiring multiple cycles of winter conditions, longer cold stratification, fire related cues (heat/smoke) [20], or possibly a longer time under suitable germination conditions to alleviate. This inherent dormancy potentially indicates that these seeds can persist in the soil seed bank under natural conditions for long periods of time and may only emerge in the standing vegetation once dormancy is alleviated and environmental conditions become suitable [38,39].…”

“…The costs of seed production and risk of recruitment failure are high in cold-climate ecosystems where growing seasons are short and nutrients generally limited [20,21]. Thus, Plants 2021, 10, 327 2 of 9 cold-climate regions are characterized by perennial, long-lived species with a dependence on clonal reproduction which emphasizes the adult life-history stages [22][23][24].…”